"Overwhelmingly, the world's climate scientists today believe that climate change is occurring and that human activities are the primary cause," the Union of Concerned Scientists report said.

Some American corporations are "talking the talk" about climate change, but aren't "walking the walk" to support efforts to address the intensifying problem of global warming, according to a report from the Union of Concerned Scientists (UCS).

Released in May, the report, "A Climate of Corporate Control: How Corporations Have Influenced the U.S. Dialogue on Climate Science and Policy," charged that some corporations are engaged in "greenwashing," a strategy in which corporations portray themselves as concerned about climate change while they seek to "undermine climate science and policy."

UCS identifies itself as "the leading science-based nonprofit working for a healthy environment and a safer world."

The UCS report said the science about climate change is clear: "Overwhelmingly, the world's climate scientists today believe that climate change is occurring and that human activities are the primary cause."

Yet some corporations have a pattern of questioning the science of climate change.

"They have been able to exert ... influence through several time-tested tactics, including: exaggerating the uncertainty associated with climate change while ignoring what is known, funding contrarian scientists and think tanks engaged in spreading misinformation and blocking policy, and contributing to politicians who proclaim they do not believe in the science of global warming," said the report.

The pattern of questioning science has long been a corporate strategy. Examples cited included the tobacco industry, which challenged the connection between cigarettes and lung cancer. Utilities expressed doubt about the science that said coal-fired plants created acid rain that harmed lakes. Asbestos companies denied the health risks of their product. Chemical companies challenged the evidence that DDT harmed wildlife.

The UCS report said corporations sometimes have contradictory positions.

General Electric was cited as an example. GE has funded both groups engaged in misinformation about climate change, such as the Heartland Institute and George C. Marshall Institute, and groups supporting climate science, such as the Worldwatch Institute.